1. Field of the Invention
The present invention relates generally to fermentation processes and systems. More particularly, the present invention relates generally to oil recovery processes and systems for fermentation systems.
2. Description of the Related Art
The production of ethanol for use as a gasoline additive or a straight liquid fuel continues to increase as petroleum costs rise and environmental concerns become more pronounced. Ethanol is generally produced using conventional fermentation processes that convert the starch in plant-based feedstocks into ethanol. While ethanol is generally the desired product produced during fermentation, there are also a number of other byproducts produced during fermentation that also have commercial value such as, for example, the oil derived from the fermentation feedstocks.
In certain fermentation processes, it can be financially lucrative to separate the oil from the fermentation product in order to recover the valuable oil. Generally, the oil is removed from the fermentation product after the ethanol has been removed therefrom. This particular fermentation product is commonly referred to as “whole stillage.” The oil is typically removed from whole stillage by processing the whole stillage in a decanter to separate it into a light phase and a heavy phase, removing the light phase from the decanter, and concentrating the light phase via evaporation until a desired solids concentration is achieved. This concentrated phase is commonly referred to as condensed distiller's solubles (“CDS”). The concentrated phase is then subjected to an oil separation step, which can involve heating, chemically treating, and centrifuging the concentrated phase. Generally, the minimum process involves centrifugation. These processes can generally recover 0.5 to 0.8 pounds of oil per bushel of grain. Unfortunately, the recovery processes described above are unable to recover a considerable portion of the oil in the fermentation product and, therefore, are unable to maximize the commercial value of the oil found in fermentation products.
Thus, there is a need for processes and systems that can maximize the recovery of the oil present in fermentation feedstocks.